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PARIS − The first swimming training session for triathletes competing at the Paris Olympics was cancelled Sunday because of pollution in the river Seine.

Whether the Seine will be clean enough to host Olympic triathlon and open-water swimming events has been a much debated topic at the Games. Paris Mayor Anne Hidalgo took a highly publicized dip in the Seine last week in a bid to ease fears. Organizers have spent more than $1.5 billion trying to overcome the river's high levels of E.coli bacteria.

The river was deemed clean enough for the swimming competitions following a series of tests in earlier this month but heavy rainfall in France's capital over the past 48 hours appears to have set that back.

In a joint statement Paris 2024 and World Triathlon said they were "confident that water quality will return to below limits before the start of the triathlon competitions," which get underway Tuesday.

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The bike and running training sessions will go ahead as planned Sunday.

In a briefing with reporters on Saturday, Scott Schnitzspahn, the U.S. Olympic triathlon team's "high performance" general manager, said he was getting updates on the Seine's water quality each day at 4 a.m. He said there is a Plan B if the river tests results don't improve. Plan B is delaying the triathlon by one day.

Plan C is the swim part of the event gets dropped altogether.

American triathlete Seth Rider revealed he has an unconventional tactic for preparing for the Seine's E. coli levels.

"We actually raced here last year in the test event," he said. "I don't think anyone got sick after that, which can't be said about all the races we do. In preparation for this race, I knew there was going to be some E.coli exposure. So I've been trying to increase my E.coli threshold by exposing myself to a bit of E.coli in day-to-day life."

One of the ways Rider claimed he's been doing that is not washing his hands after he goes to the bathroom.

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